Method for low temperature chemical vapor deposition of low-k films using selected cyclosiloxane and ozone gases for semiconductor applications

ABSTRACT

A method is described for forming a low-k dielectric film, in particular, a pre-metal dielectric (PMD) on a semiconductor wafer which has good gap-filling characteristics. The method uses a thermal sub-atmospheric CVD process that includes a carbon-containing organometallic precusor such as TMCTS or OMCTS, an ozone-containing gas, and a source of dopants for gettering alkali elements and for lowering the reflow temperature of the dielectric while attaining the desired low-k and gap-filling properties of the dielectric film. Phosphorous is a preferred dopant for gettering alkali elements such as sodium. Additional dopants for lowering the reflow temperature include, but are not limited to boron, germanium, arsenic, fluorine or combinations thereof.

FIELD OF THE INVENTION

[0001] The present invention relates to semiconductor processing, andmore particularly to a process for forming a blanket dielectric layer tofill gaps between device elements.

BACKGROUND OF THE INVENTION

[0002] In the manufacturing of semiconductor devices, as the dimensionshave shrunk, it has become more challenging to provide dielectric filmlayers that provide adequate electrical isolation between interconnectfeatures and device components in order to minimize RC delay andcrosstalk. One method of doing this is to provide dielectric layersusing materials having lower dielectric constants (low-k dielectrics)than conventional dielectric materials such as silicon dioxide (SiO₂) orsilicon nitride. Low-k dielectrics typically have dielectric constantsbelow about 4, where air has a dielectric constant of 1.

[0003] In particular, at the start of the fabrication of a back end ofline (BEOL) module which contains the interconnect metal levels, adielectric layer is typically provided between the devices or features,such as gate conductor stacks, on the substrate, or front end of line(FEOL), and the first layer of metal in the interconnect level or BEOL.This dielectric layer between the device level and the interconnectlevel is known as the pre-metal dielectric (PMD). The process of formingthis PMD is referred to hereinafter as a middle of line process, or MOLprocess, as opposed to the BEOL processes used to form the intermetaldielectrics (IMD) that separate the metal layers.

[0004] Methods of depositing low-k dielectric blanket layers haveincluded spin-on, chemical vapor deposition (CVD), and plasma-enchancedchemical vapor deposition (PECVD), with PECVD more recently preferred.PECVD processes include the use of organosilicon precursors, such asmethylsilane (1MS), trimethyl silane (3MS) and tetramethylsilane (4MS),with various oxidizers. However, the CVD processes, in particular PECVD,may not adequately fill the spaces or gaps between existing metalfeatures, and may leave voids in the dielectric blanket layer which cancause problems such as micro-cracking, lack of structural support,trapping of gases or moisture or allow subsequent metal fill processesto connect nearby voids which can result in shorted device elements.Although films provided by spin-on deposition may adequately fill spacesor gaps, these films are usually porous and would be incompatible withother MOL processing steps by being susceptible to problems such asthose mentioned above. The problem of adequate gap fill can beparticularly difficult if the aspect ratio (AR), which is the ratio ofheight to width of the gaps, is above about 1.0. For example, referringto FIG. 1, device structures 130 are formed over a doped region 120 on asubstrate 110. The device structures 130, such as gate conductor stacks,are separated by width W and each have height H. Therefore the gap 160separating the device structures 130 has an aspect ratio (AR) of H/W. IfH is greater than W, then the AR is greater than 1 and a blanketdielectric layer 140 formed by a conventional PECVD process will notcompletely fill the gap 160, leaving a void 150, which can causeproblems such as structural and electrical defects as mentioned above.

[0005] PECVD methods for depositing low-k dielectric layers for BEOLlevels have been suggested which use a carbon-containing precursor, forexample, a cyclosiloxane such as tetramethylcyclo-tetrasiloxane (TMCTS)or methylsilanes, with oxygen. Low-k dielectrics will also be requiredat the MOL level. PECVD can provide deposition rates which are fastenough (in the range of 100's to 1000's Å/min) for BEOL applicationswhich must operate at temperatures below about 400° C., and as low as300° C., because of the presence of metal features. However, PECVDsolutions at the MOL level are not easily utilized, because PECVDprocesses may leave voids in high aspect ratio gaps, where the gap ARexceeds about 1.0. In addition, plasma processing is not a preferredfill method for MOL as it may cause charge damage to gate oxides.

[0006] Thermal CVD processes do not require the use of plasmas todeposit dielectric layers. Sub-atmospheric thermal CVD (SACVD) and lowpressure thermal CVD have been used for providing conformal depositionof dielectrics, in which O₃ and O₂ are respectively used as oxidizingagents. The pressure in SACVD is in the range from about 50 to 800 Torr,and usually between about 200 to 760 Torr. Low pressure CVD typicallyinvolves pressures below about 10 Torr.

[0007] Low pressure CVD will not provide good gap filling results forchemistry such as oxygen plus an organometallic or organosiliconprecursor such as TMCTS. Good gap filling typically results through theuse of SACVD at pressures above about 200 Torr, and more likely aboveabout 600 Torr. However, using low-k materials for AR greater than 1,SACVD may also leave voids depending on the shape of the gap to befilled.

[0008] It would be desirable to use a post-deposition glass reflow stepat a low reflow temperature to fill voids left after deposition of alow-k film with minimal heat treatment to avoid thermal damage. Forexample, in the case of conventional (high-k) dielectric films wherecontrolling the dielectric constant has not been a design requirement,it is known that the addition of dopants may lower the temperaturerequired to reflow the film. However, because the process conditions fordepositing low-k films that would also provide good gap-filling resultsare quite sensitive to the composition of reactant gases and thestructure of the gaps to be filled, the addition of dopants which reducethe reflow temperature would not necessarily preserve the desired low-kand gap-filling properties of the film, and may require significantexperimentation to achieve the desired results.

[0009] Thus, there is a need for a non-plasma low-k oxide CVD processthat can provide good gap-filling results for AR greater than 1, thatavoids charge damage, that can getter alkali elements, that can bereflowed with minimal heat treatment to avoid thermal damage to theunderlying device elements, and that provides a film having the desiredlow-k property.

[0010] Sukharev (U.S. Pat. No. 5,710,079, hereinafter, the Sukharevpatent) discloses a method for depositing silicon dioxide films toprevent the formation of voids in gaps by CVD with an organometalliccompound, such as tetraethylorthosilicate (TEOS), BPTEOS, TEB, TMOP,OMCTS, HMDS, TMCTS, or TRIES, and which includes ozone and the use ofultraviolet radiation (UV) to increase the deposition rate by increasingthe concentration of hydroxyl radicals in order to avoid the formationof voids and improve gap-fill. However, the increased concentration ofhydroxyl radicals may lead to a porous film that is incompatible withMOL processing and increased concentration of hydroxyl radicals willresult in reduced carbon incorporation in the film. Since carbonincorporation is required to achieve a low-k oxide, the Sukarev patentdoes not provide a solution for depositing low-k dielectric films thatprovide good gap filling results. Moreover, the use of UV radiation toincrease deposition rates may require modification of standard reactionchambers and may increase the cost of processing.

[0011] Yuan (U.S. Pat. No. 5,855,957, hereinafter, the Yuan patent)discloses a method for depositing an oxide thin film using anatomospheric pressure thermal CVD (APCVD) process including ozone (O₃)which can provide uniform step coverage. The Yuan patent discloses theuse of precursors such as tetraethoxysilane (TEOS), hexamethyldisilazane(HMDSO), octamethylcyclotetrasiloxane (OMCTS),2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS), substances of the generalformula SiH_(x)(OR)_(4-x) where “R” is an alkyl group or its oligomersand x=0, 1, 2, or 3, and other chemicals such as boron, phosphorous,fluorine containing sources and combinations thereof. The method of theYuan patent discloses that uniform step coverage or gap fill can beprovided for AR up to about 3. In addition, the preferred embodiment ofthe Yuan patent requires movement of the wafer through the reactor,which adds to the complexity of the reactor design. Movement of thewafer also results in variation in elemental composition with depthacross the substrate and therefore the etch rate will vary with depth,which is incompatible with MOL processing steps such as wet HF etch. Inaddition, the Yuan patent is not directed to the deposition of low-kdielectric films, which would require strict compositional and densitycontrol that is beyond the capability of the Yuan patent.

[0012] Saito (U.S. Pat. No. 5,545,436, hereinafter, the Saito patent)discloses an atmospheric CVD method including O₃ for depositing anundoped silicon oxide film using a precursor such as TEOS, OMCTS, tetrapropoxy silane (TPOS), or TMCTS. The Saito patent also requires themovement of the wafer relative to the gas injector, adding complexity tothe reactor design and suffers from similar compositional deficienciesas in the Yuan patent. Therefore, the Saito patent is not suitable forthe deposition of low-k dielectrics that provide good gap-filling for ARgreater than about 3.

[0013] Rose et al. (U.S. Pat. No. 6,068,884, hereinafter, the Rosepatent) discloses a method for depositing a low-k dielectric film usinga PECVD process. The Rose patent discloses the use of precursors oforganosilicon, such as siloxanes, to form an inorganic/organic hybriddielectric material having a low-k (less than 4.0, and preferably in therange 3.0 to 1.5) and good thermal stability at temperatures in therange of 425-450° C. The precursors disclosed in the Rose patent includeorganic siloxanes, fluorosiloxanes, cyclosiloxanes, fluorine containingcyclosiloxanes, organosilazanes, fluorosilazanes, cyclosilazane,silicates, TEOS, and TMS and mixtures thereof. Although the Rose patentsuggests that either atmospheric, subatmospheric, or low pressurethermal CVD processes may be used, the preferred embodiments of the Rosepatent require the use of a plasma CVD process with organosiliconprecursors such as hexamethyl disiloxane (HMDSO),1,1,3,3-tetramethyldisiloxane (TMDSO), TEOS, and OMCTS. Thus, the methodof the Rose patent does not recognize the disadvantage of potentialcharge damage due to the use of plasma CVD processes. The Rose patentalso does not solve the problem of gap-fill for AR greater than 1.

[0014] Ravi et al. (U.S. Pat. No. 5,976,993, hereinafter, the Ravipatent) discloses a method for depositing silicon oxide films withreduced instrinsic stress which can also provide good gap-fill resultsusing a high density plasma chemical vapor deposition (HDPCVD) process.Since the Ravi patent teaches the use of a PECVD process and does notsuggest the use of a carbon-containing cyclosiloxane precursor such asTMCTS or OMCTS, the Ravi patent is not suitable for depositing low-kdielectric films which have good gap fill characteristics for AR greaterthan about 1. Also, the method of the Ravi patent suffers from potentialcharge damage due to plasma processing.

[0015] Laboda et al. (EP 0 960 958 A2, hereinafter, the Labodareference) discloses a method for depositing low-k dielectric filmsusing a plasma enhanced CVD (PECVD) or ozone enhanced CVD process usinga methyl-containing silane, such as methylsilane, dimethylsilane,trimethylsilane and tetramethylsilane, and an oxygen providing gas. TheLaboda reference also suggests that dopants such as phosphine ordiborane, halogens such as fluorine may be used, but does not suggestwhat advantages such dopants might provide. The Laboda reference alsodoes not recognize the problem of potential charge damage due to plasmaprocesses. In addition, the method of the Laboda reference does notprovide good gap-filling characteristics for AR greater than about 1.

[0016] In view of the foregoing discussion, there is a need to providefor a method to deposit a low-k dielectric PMD layer that can fill highaspect ratio (AR greater than about 3) gaps without voids, withoutcharge or thermal damage to the semiconductor devices and providesgettering of alkali elements.

SUMMARY OF THE INVENTION

[0017] The present invention addresses the above-described need byproviding a method for depositing a pre-metal low-k dielectric thatprovides good gap fill, minimizes the formation of voids, and gettersalkali elements such as sodium and potassium.

[0018] It is the further object of the present invention to provide amethod for forming a pre-metal low-k dielectric by a process which willnot cause thermal damage to the semiconductor devices by keeping theprocess temperature within the thermal budget of the devices.

[0019] This invention has the further objective of forming a pre-metallow-k dielectric by a process which will not cause charge damage to thesemiconductor devices.

[0020] According to one aspect of the present invention, a method isprovided for forming a pre-metal (PMD) low-k dielectric layer by athermal sub-atmospheric chemical vapor deposition process including acarbon-containing precursor, ozone, and a source of dopants.

[0021] The novel features believed to be characteristic of thisinvention are set forth in the appended claims. The invention itself,however, as well as other objects and advantages thereof, may be bestunderstood by reference to the following detailed description of anillustrated preferred embodiment to be read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 illustrates a prior art blanket dielectric layer having avoid.

[0023]FIG. 2 illustrates a single wafer CVD reactor which can be used toimplement the process of depositing a pre-metal dielectric layer inaccordance with the present invention.

[0024]FIG. 3 is a flow chart showing the steps of a preferred embodimentfor depositing a pre-metal dielectric layer in accordance with thepresent invention.

[0025]FIG. 4 illustrates a pre-metal dielectric layer formed inaccordance with the present invention, having good gap fillcharacteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In the following descriptions of the preferred embodiments of theinvention, a method for depositing a pre-metal dielectric layer atmiddle of line will be detailed. It will be appreciated that this isintended as an example only, and that the invention may be practicedunder a variety of conditions and using a variety of precursors.

[0027] In a preferred embodiment of the present invention, the method offorming a pre-metal (PMD) low-k dielectric layer uses a thermalsub-atmospheric chemical vapor deposition process which includes acarbon-containing organometallic or organosilicon precursor, ozone, anda source of dopants. The carbon-containing organometallic ororganosilicon precusors may include a cyclosiloxane such astetramethycyclo-tetrasiloxane (TMCTS) or orthomethylcyclo-tetrasiloxane(OMCTS), or other cyclic siloxanes. A dielectric constant of less thanabout 3.0 is expected due to the carbon content provided by theprecursor and the microstructure of the film thereby provided. Aphosphorous dopant is added to getter alkali metals such as sodium andpotassium. In addition to phosphorous, a dopant is added that allows thefilm to reflow relatively easily at a temperature and process time thatwill not lead to thermal damage. As the AR increases, the formation ofvoids becomes more likely, and some reflow may be necessary. For 0.1μgeneration devices, the thermal reflow cycle is preferably in the rangeof temperature less than about 725° C. for about 20 minutes, which willnot cause thermal damage at the PMD level. In a preferred embodiment ofthe present invention, dopants such as phosphorous and boron are addedwhich will lower the reflow temperature required to fill a given AR gapwithout thermal damage. Phosphorous is required in order to getteralkali elements, and also acts to lower the reflow temperature to someextent, but typically not sufficiently to avoid thermal damage.Additional dopants that act to further lower the reflow temperatureinclude, but are not limited to boron, germanium, arsenic, fluorine orcombinations thereof.

[0028] Referring to FIG. 2 and FIG. 3, the method in accordance with thepresent invention can be performed in a conventional single wafer CVDreactor 200 shown in FIG. 2, which is provided as in Process Step 320 inFIG. 3. In Process Step 330, a wafer 210 is provided, which may havesemiconductor device features on it, and is placed within the reactor200 on a platform 220 which includes a heating element therein (notshown), controlled by a heater suscepter 230 which is used to controlthe temperature within the reactor 200. All reactor components aremaintained at predetermined temperatures as indicated by Process Step340 of FIG. 3. In accordance with the present invention, flow ofreaction gases is supplied in Process Step 350, including at least acarbon-containing organometallic precursor 260 (Process Step 352), amixture of oxygen and ozone 270 (Process Step 356), and a source ofdopants 280 (Process Step 354), is supplied to a pre-mixing chamber 250,and the mixture of gases is applied to the wafer 210. In the preferredembodiment of the present invention, improved gap-filling results havebeen obtained by premixing the gases within a pre-mixing chamber 250which acts to initiate the reaction and obtain the desired filmproperties. Alternatively, the gases can be released separately into thereactor volume without premixing, but at a predetermined distance fromthe wafer surface, for example about 50-500 mils (about 0.05-0.5inches). However, this post-mixing alternative will result in a filmhaving less than optimal properties. A pump 240 is used to control andmaintain the pressure within the reactor 200 to a predetermined pressure(Process Step 360). The gas mixture is applied to the wafer for aredetermined time (Process Step 370) to form the blanket low-kdielectric layer 170 which has good gap-fill characteristics, as shownin FIG. 4. Finally, in Process Step 380, any excess gases are removedfrom the chamber.

[0029] The carbon-containing precursor is preferably TMCTS, but could beany carbon-containing precursor such as OMCTS or the like. The source ofdopants could include triethylphosphate (TEPO) which is a source ofphosphorous, and triethylborate (TEB) which is a source of boron. Thepresence of phosphorous as a dopant has the benefit of gettering foralkali elements such as sodium. A phosphorous dopant also tends to lowerthe reflow temperature, but is typically not sufficient by itself toreduce the reflow temperature so that thermal damage is avoided. In thepreferred embodiment of the present invention, the additional dopant,boron, is added to lower the temperature at which reflow can occur inorder to avoid thermal damage. Dopants added for the purpose of loweringthe reflow temperature in accordance with the present invention couldinclude, but are not limited to, boron, germanium, arsenic, fluorine orcombinations thereof. Germanium may be supplied by a precursor such astetramethylgermane, or the like. Arsenic may be supplied by a precursorsuch as tetramethylarsine, or the like. Fluorine may be supplied byfluorinated analogs of TMCTS, or the like.

[0030] Process conditions for this embodiment include a temperature inthe range of about 100-700° C., preferably from about 500-600° C. Thepressure in accordance with the present invention is in the range of50-800 Torr, preferably from about 200-700 Torr. The best results areexpected using pressures of about 600-700 Torr. However, pressures aslow as 200 Torr may be used. The process includes flow of a gascomprising a mixture of oxygen (O₂) and ozone (O₃) in the range of1000-10000 sccm, preferably about 5000 sccm, and where the concentrationof ozone (O₃) in the O₂ flow is between about 5-20 wt %, preferablyabout 15 wt %. TMCTS flow is in the range of about 100-10000 mgm,preferably about 100-500 mgm. The triethylborate (TEB) flow is in therange of about 100-500 sccm, and the triethylphosphate (TEPO) flow is inthe range of about 10-100 sccm. The preferred resulting PMD low-kdielectric layer should have a boron concentration from about 0-6%, andpreferably about 4%, and have a phosphorous concentration from about2-5%, and preferably about 4%.

[0031] While the invention has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Accordingly, the invention is intended toencompass all such alternatives, modifications and variations which fallwithin the scope and spirit of the invention and the following claims.

We claim:
 1. A method for depositing a dielectric film comprising the steps of: providing a chemical vapor deposition (CVD) reaction chamber; providing a semiconductor wafer within said reaction chamber, said wafer having features on a surface of said wafer, wherein said features are spaced to form at least one gap between said features; providing a carbon-containing organometallic precursor; providing an ozone-containing gas; providing a dopant-containing gas; and reacting said precursor, said ozone-containing gas and said dopant-containing gas, to deposit a low-k film on said surface, so that said low-k film substantially fills said at least one gap.
 2. The method of claim 1 wherein said gap has an aspect ratio greater than about
 3. 3. The method of claim 1 wherein said low-k film has a dielectric constant of less than about
 3. 4. The method of claim 1 wherein said CVD reaction chamber is a single wafer reactor.
 5. The method of claim 1 further comprising the step of premixing said carbon-containing organometallic precursor, said ozone-containing gas, and said dopant-containing gas prior to said step of reacting.
 6. The method of claim 1 wherein said step of reacting comprises thermal sub-atmospheric pressure chemical vapor deposition.
 7. The method of claim 1 further comprising the step of reflowing said low-k film.
 8. The method of claim 7 wherein said step of reflowing is performed at a temperature less than about 725° C. for about 20 minutes.
 9. The method of claim 1 wherein said carbon-containing precursor is selected from the group consisting of TMCTS and OMCTS.
 10. The method of claim 1 wherein said step of providing a carbon-containing precursor comprises TMCTS flow between about 100 to about 10,000 mgm.
 11. The method of claim 1 wherein said step of providing a carbon-containing precursor comprises TMCTS flow between about 100 to about 500 mgm.
 12. The method of claim 1 wherein said step of providing an ozone-containing gas comprises flow of a mixture of oxygen and ozone from about 1000 to about 10,000 sccm.
 13. The method of claim 12 wherein said ozone is between about 5 to 20 wt % of said mixture of oxygen and ozone.
 14. The method of claim 12 wherein said ozone is about 15 wt % of said mixture of oxygen and ozone.
 15. The method of claim 1 wherein said step of providing an ozone-containing gas comprises flow of a mixture of oxygen and ozone of about 5000 sccm.
 16. The method of claim 15 wherein said ozone is between about 5 to 20 wt % of said mixture of oxygen and ozone.
 17. The method of claim 15 wherein said ozone is about 15 wt % of said mixture of oxygen and ozone.
 18. The method of claim 1 wherein said step of providing a dopant-containing gas comprises TEB flow and TEPO flow.
 19. The method of claim 18 wherein said TEB flow is between about 100 to about 500 sccm and said TEPO flow is between about 10 to about 100 sccm.
 20. The method of claim 1 wherein said dopant-containing gas includes a dopant selected from the group consisting of phosphorous, boron, germanium, arsenic, fluorine and a combination thereof.
 21. The method of claim 1 wherein said dopant-containing gas includes phosphorous and further includes a second dopant selected from the group consisting of boron, germanium, arsenic, fluorine and a combination thereof.
 22. The method of claim 1 further comprising the step of pre-heating said reactor to a predetermined temperature following said step of providing a wafer.
 23. The method of claim 22 wherein said predetermined temperature is between about 100-700° C.
 24. The method of claim 1 wherein said step of reacting said precursor further comprises achieving and maintaining a predetermined pressure.
 25. The method of claim 24 wherein said predetermined pressure is between about 50 to about 800 Torr.
 26. The method of claim 24 wherein said predetermined pressure is between about 200 to about 700 Torr.
 27. A method for depositing a dielectric film comprising the steps of: providing a chemical vapor deposition (CVD) reaction chamber; providing a semiconductor wafer within said reaction chamber, said wafer having features on a surface of said wafer, wherein said features are spaced to form at least one gap between said features; preheating said reaction chamber to a predetermined temperature of about 500-600° C.; providing a carbon-containing organometallic precursor selected from the group consisting of TMCTS and OMCTS; providing an ozone-containing gas flowing at about 5000 sccm, wherein said ozone-containing gas comprises oxygen and ozone, wherein said ozone has a concentration of about 15 wt %; providing a dopant-containing gas including TEB flowing between about 100-500 sccm and TEPO flowing between about 10-100 sccm; and reacting said precursor, said ozone-containing gas and said dopant-containing gas at a pressure between about 200-700 Torr to deposit a low-k film on said surface, so that said low-k film substantially fills said at least one gap.
 28. The method of claim 27 further comprising the step of premixing carbon-containing organometallic precursor, said ozone-containing gas, and said dopant-containing gas prior to said step of reacting.
 29. The method of claim 27 wherein said gap has an aspect ratio greater than about
 3. 30. The method of claim 27 wherein said low-k film has a dielectric constant of less than about
 3. 31. The method of claim 27 further comprising the step of reflowing said low-k film.
 32. The method of claim 31 wherein said step of reflowing is performed at a temperature less than about 725° C. for about 20 minutes.
 33. A pre-metal dielectric (PMD) semiconductor structure comprising: a semiconductor wafer having features on a surface of said wafer, wherein said features are spaced to form at least one gap between said features; and a low-k film covering said surface, wherein said low-k film fills said at least one gap without having a void, and said low-k film includes a dopant.
 34. The PMD structure of claim 33 wherein said at least one gap has an aspect ratio greater than about
 3. 35. The PMD structure of claim 33 wherein said low-k film has a dielectric constant less than about
 3. 36. The PMD structure of claim 33 wherein said dopant comprises phosphorous.
 37. The PMD structure of claim 36 wherein said dopant further comprises a second dopant selected from the group consisting of boron, germanium, arsenic, fluorine and a combination thereof.
 38. The PMD structure of claim 33 wherein said features comprise gate conductor stacks.
 39. The PMD structure of claim 33 wherein said low-k film has a reflow temperature less than about 725° C.
 40. A pre-metal dielectric (PMD) semiconductor structure comprising: a semiconductor wafer having gate conductor stacks on a surface of said wafer, said gate conductor stacks spaced to form at least one gap having an aspect ratio greater than about 3; and a low-k film covering said surface, said low-k film having a dielectric constant less than about 3, wherein said low-k film fills said at least one gap without having a void and wherein said low-k film includes phosphorous and a dopant selected from the group consisting of boron, germanium, arsenic, fluorine and a combination thereof.
 41. A low-k film comprising: a carbon-containing dielectric material; phosphorous; and a dopant selected from the group consisting of boron, germanium, arsenic, fluorine and a combination thereof, wherein said low-k film has a dielectric constant less than about 3 and having a reflow temperature less than about 725° C. 